Collins’ comments come amid wide speculation about a Republican primary bid against Trump, who remains very popular among Republican voters. Ohio Gov. John Kasich, who was defeated easily by Trump in 2016, has encouraged speculation he will challenge the president in 2020, traveling to New Hampshire this fall. Collins supported Kasich in the 2016 election and said in August 2016 that she would not be voting for Trump in that election.

Sen. Jeff Flake, R-Arizona, has also been floated as a potential candidate to oppose Trump in a primary, although the senator said this November, “I don’t think that will be me. I think there are better candidates out there.”

Earlier this month, Trump brushed off the danger of a potential primary challenge, encouraging Kasich and Flake to get into the race. The last two presidents to only serve one term – George H.W. Bush and Jimmy Carter – both faced primary challengers.